The people of Serbia are making a fourth bid to elect a new president. This time, the rules have been changed to ensure there is a winner. Public opinion polls indicate it could be the candidate from the nationalist right, a political ally of former President Slobodan Milosevic, who is on trial on war crimes charges.

To prepare for this election, the Serbian parliament abolished a law that required a minimum turnout of 50 percent to validate a presidential poll. That requirement resulted in the failure of three previous election attempts, and left Serbia without a president for the past year-and-a-half.

None of the 15 candidates is expected to get more than half of the votes, forcing a run-off later in the month between the top two.

Public opinion polls say the leading candidate will be nationalist Tomislav Nikolic, of the Serbian Radical Party, which was allied with the former president of Serbia and later Yugoslavia, Slobodan Milosevic, who is the most prominent person on trial at the U.N. War Crimes Tribunal in The Hague. Radical Party leader Vojislav Seselj is also on trial at the Tribunal.

Western nations have expressed concern at the prospect Mr. Nikolic might become Serbia's president. They say it would scare away investors and postpone the date that Serbia, and its partner Montenegro, could join the European Union. In addition, the United States and other countries have linked millions of dollars in Western aid to Serbia's cooperation with the U.N. War Crimes Tribunal.

Mr. Nikolic's Serbian Radical Party despises that institution, and he has said Serbs wanted by the Tribunal should only be encouraged to surrender, not captured and extradited as the court has demanded.

Although the powers of the Serbian president are limited, analysts say a victory by Mr. Nikolic could bring down the minority reformist government of the more pro-Western Serbian prime minister, Vojislav Kostunica.

Mr. Kostunica needs the support of Mr. Nikolic's Radical Party to stay in office. The prime minister has recently changed his policy on the War Crimes Tribunal, calling for "serious cooperation" with it, in order to promote Serbia's integration into Europe.

Mr. Nikolic is likely to face a run-off in two weeks against the soft spoken pro-Western Democratic Party chief Boris Tadic. The Democrats are still trying to heal the wounds from the assassination last year of Zoran Djindjic, their leader and Serbia's first non-communist prime minister since World War I.

Bogoljub Karic, a millionaire tycoon whose business empire includes a cell phone network, a bank, a large construction company and a television station, was expected to come in third, despite his promise to revive Serbia's economy. The candidate of Prime Minister Kostunica's ruling coalition, former parliamentary speaker Dragan Marsicanin, has slipped to fourth in the public-opinion polls.